2010A&A...520A...8L


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.23CEST01:00:01

2010A&A...520A...8L - Astronomy and Astrophysics, volume 520, A8-8 (2010/9-2)

Planck pre-launch status: expected LFI polarisation capability.

LEAHY J.P., BERSANELLI M., D'ARCANGELO O., GANGA K., LEACH S.M., MOSS A., KEIHAENEN E., KESKITALO R., KURKI-SUONIO H., POUTANEN T., SANDRI M., SCOTT D., TAUBER J., VALENZIANO L., VILLA F., WILKINSON A., ZONCA A., BACCIGALUPI C., BORRILL J., BUTLER R.C., CUTTAIA F., DAVIS R.J., FRAILIS M., FRANCESCHI E., GALEOTTA S., GREGORIO A., LEONARDI R., MANDOLESI N., MARIS M., MEINHOLD P., MENDES L., MENNELLA A., MORGANTE G., PREZEAU G., ROCHA G., STRINGHETTI L., TERENZI L. and TOMASI M.

Abstract (from CDS):

We present a system-level description of the Low Frequency Instrument (LFI) considered as a differencing polarimeter, and evaluate its expected performance. The LFI is one of the two instruments on board the ESA Planck mission to study the cosmic microwave background. It consists of a set of 22 radiometers sensitive to linear polarisation, arranged in orthogonally-oriented pairs connected to 11 feed horns operating at 30, 44 and 70GHz. In our analysis, the generic Jones and Mueller-matrix formulations for polarimetry are adapted to the special case of the LFI. Laboratory measurements of flight components are combined with optical simulations of the telescope to investigate the values and uncertainties in the system parameters affecting polarisation response.
Method. of correcting residual systematic errors are also briefly discussed. The LFI has beam-integrated polarisation efficiency >99% for all detectors, with uncertainties below 0.1%. Indirect assessment of polarisation position angles suggests that uncertainties are generally less than 0.5° and this will be checked in flight using observations of the Crab nebula. Leakage of total intensity into the polarisation signal is generally well below the thermal noise level except for bright Galactic emission, where the dominant effect is likely to be spectral-dependent terms due to bandpass mismatch between the two detectors behind each feed, contributing typically 1-3% leakage of foreground total intensity. Comparable leakage from compact features occurs due to beam mismatch, but this averages to <5x10–4 for large-scale emission. An inevitable feature of the LFI design is that the two components of the linear polarisation are recovered from elliptical beams which differ substantially in orientation. This distorts the recovered polarisation and its angular power spectrum, and several methods are being developed to correct the effect, both in the power spectrum and in the sky maps. The LFI will return a high-quality measurement of the CMB polarisation, limited mainly by thermal noise. To meet our aspiration of measuring polarisation at the 1% level, further analysis of flight and ground data is required. We are still researching the most effective techniques for correcting subtle artefacts in polarisation; in particular the correction of bandpass mismatch effects is a formidable challenge, as it requires multi-band analysis to estimate the spectral indices that control the leakage.

Abstract Copyright:

Journal keyword(s): polarization - instrumentation: polarimeters - space vehicles: instruments - techniques: polarimetric - cosmic microwave background

Simbad objects: 6

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Number of rows : 6

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 V* CM Tau Psr 05 34 31.93830 +22 00 52.1758           F 4711 1
2 M 1 SNR 05 34 31.94 +22 00 52.2           ~ 5486 4
3 NAME Ori Complex Cld 05 35.3 -05 23           ~ 316 0
4 NAME SEP reg 06 00 00.000 -66 33 38.55           ~ 108 0
5 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3615 1
6 NAME NEP reg 18 00 00.000 +66 33 38.55           ~ 246 0

    Equat.    Gal    SGal    Ecl

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2019.10.23-01:00:01

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